[aprssig] Mobile Digi (TEMPn-N)
mckeehan at mckeehan.homeip.net
Mon Jun 15 13:26:56 CDT 2009
Thank you Stephen! This is exactly the type of response that I was looking for.
On Mon, June 15, 2009 1:13 pm, Stephen H. Smith wrote:
> William McKeehan wrote:
>> Why would it be a bad idea for the D700's to run around with WIDE1-1 enabled
>> all of the time?
> 1) You wind up with an unstable, constantly-changing network as
> mobiles move around:
> o Either the fixed digipeaters cover an area adequately, in which
> case extra mobile digis are irrelevant and just add channel congestion .
> o The fixed infrastructure does have coverage holes, but users can
> never count on fill-in coverage at given locations since mobiles are
> constantly moving around.
> 2) You get massive numbers of unnecessary additional digipeats most of
> the time, resulting in a massive increase in channel loading. Imagine
> the QRM mess and amount of air time consumed if 5 or 10 mobiles a few
> miles apart in the afternoon rush hour all try to digipeat each other's
> packets constantly. Then consider the hundreds of duplicate packets
> hitting the local WIDEs from all those mobile digipeats added to the
> home fill-in digipeats.
> 3) For everyday use, mobiles make terrible digis since they:
> o Are lower to the ground than even home WIDE1-1 fill-in digis, and
> lack useful antenna height.
> o Are usually moving. The data bit-error rate (which causes RX and
> TX failures) due to mobile flutter goes up rapidly as the speed increases.
> BOTTOM LINE: Unless a mobile is PARKED and STATIONARY on high ground
> (hill top, top of a parking ramp, etc), they are adding to the problem
> (by creating channel congestion, and possibly adding to the number of
> defective packets) rather than helping.
> Stephen H. Smith wa8lmf (at) aol.com
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